1. Field of the Invention
The invention relates to the technical field of formulations of active substances.
2. Description of Related Art
Active substances can in principle be formulated in a great variety of ways, wherein the properties of the active substances and the nature of the formulation can throw up problems with regard to the producibility, stability, usability and effectiveness of the formulations. In addition, for economic and ecological reasons certain formulations are more advantageous than others.
Water-based formulations, such as aqueous suspension concentrates (SC), as a rule have the advantage that they require a low to zero content of organic solvents. Aqueous suspension concentrates for the formulation of active substances are known from the agrochemicals field. Thus for example aqueous suspension concentrates of pesticides are described in EP 0110174 A. Here a mixture of formaldehyde condensation products or ligninsulfonates and wetting agents is preferably used.
Apart from this, there is in general a demand for highly concentrated formulations of active substances, since the higher concentration has many advantages. Thus for example with highly concentrated formulations a lower expenditure on packaging is necessary than with less concentrated formulations. Similarly, the expenditure for production, transport and storage decreases; also, for example, the preparation of the spraying mixtures is simplified owing to the smaller quantities of for example pesticides which have to be handled, e.g. in the filling and mixing process.
More highly concentrated aqueous suspension concentrates are known, such as for example of sulfur (EP 0220655 A), which is based on mixtures of formaldehyde condensation products, preferably ligninsulfonates and wetting agents.
The active substances from the 1,2,4-triazinones group, such as metamitron and metribuzin, are highly effective herbicides with activity against harmful plants in plant crops. For the active substance metamitron, EP 0620971 A1 describes a more highly concentrated aqueous suspension concentrate based on mixtures of ethoxylated, optionally phosphate group-containing tristyrene- and alkyl-phenols and ligninsulfonate salts. However, the use of these formulation approaches, described in EP 0620971 A1, for the active substance metribuzin did not lead to the desired results. The reasons for this may be on the one hand because metribuzin is less easily wettable than metamitron. EP 1790228 A1 describes how a more highly concentrated aqueous suspension concentrate can be produced for the active substance metribuzin by the use of a mixture of surfactants based on substituted phenol ethers with aluminum silicate-based thickeners, such as for example attapulgite. However, according to reports from the IRAC (International Agency for Research on Cancer), there are possible health risks, depending on the particle length of the attapulgite. Attempts on the basis of the formula of the aluminum silicate-free SC formulation currently on the market, with 480 g metribuzin active substance content/L, which corresponds to 41 weight percent (wt. %), to load this with active substance contents of more than 500 g active substance/L (correspond to ca. 43 wt. %), were unsuccessful. Thus, the milling process by means of bead mills was found to be unworkable since immediate solidification took place.
The task was now to provide formulations for the active substance metribuzin with a high active substance concentration, which are aluminum silicate-free and which have advantageous properties such as storage stability and low viscosity.
As well as this, a stable dispersion in the spray mixture is required, in which the highly diluted active substance concentration must be stable for several hours before application. Such requirements for the stability of dispersions in spray mixtures do not arise at all for formulations for seed treatment (seed dressings, ‘seed-treatment formulations or compositions’), since these are applied directly onto the seeds either concentrated or only slightly diluted. Thus publications from this field, such as for example WO 2009/021985 A2, which exclusively relates to ‘seed-treatment compositions’, provide no suitable technical teaching whatever for the maintenance of stable dispersions in the spray mixture.